Personally, I’m waiting for Peter Martin at Cornell to update his excellent Bluebook® Cheat Sheet. But, if you want to know all things Bluebook®, I can recommend this website – https://www.legalbluebook.com/.
This website also provides a way to buy a hard copy, which is my preference when I use it regularly. If you use The Bluebook® at all, I recommend bookmarking and browsing here the entire website and its features. Yearly subscriptions are a reasonable rate.
The good news for Bluebook® users is that, at the beginning of every new edition, there is a list of the differences between this version and the last one. Here is a preview of what is new in the 20th Edition: https://www.legalbluebook.com/Public/Updates.aspx.
Yes, you will wonder about why some of the changes were made. That is a given. But isn’t it nice to have all the changes summarized and listed for you right up front. No guessing and no reason to search the entire book to find the updates. -CCE